Conventional bearings are designed to take pure radial loads, pure thrust loads or combination percentages of radial and thrust loads. A single row deep groove bearing incorporating bearing balls will take radial loads and some thrust loads and can be designed with angled contact surfaces to take increased thrust loads. A ball type bearing can also be configured to take thrust loads only whilst straight roller type bearings can take radial loads but cannot take thrust loads. Roller bearings can be configured with tapered rollers and can take radial or thrust loads or a combination percentages of radial and thrust loads however they are unsuited to taking bi-directional thrust loadings. When this type of load is encountered, it is necessary to use combinations of opposed tapered roller, axial contact ball, and barrel roller bearings.
Conveyor idler rolls as used for example in supporting conveyor belts in the mining industry include a tubular body and an axle which extends through the body and which is supported adjacent each end to the tubular body by bearings. Generally, the bearings used are conventional reduced friction plain, angular contact ball, deep grooved ball, roller or taper roller bearings. Separate thrust bearings may also be provided being located on the shaft with the inner races of the bearings being a part of or located on a stepped section of the shaft and held in position by thrust collars, circlips or nuts or alternatively being a pressed fit onto the shaft.
Conventional idler rolls which have axles extending through the body of the idler are of substantial weight raising issues relating to lifting and carrying weights under Occupational Work Place Health & Safety legislation.
As far as the applicant is aware, stub axle assemblies have not commonly been applied to use in conveyor idler roll application but if used their axial length would be vastly increased to accommodate bearing alignment constraints. Such assemblies would require back to back or opposed thrust bearings and/or combinations thereof with separators, spacer collars or shoulders on either axial shaft, hub/disc or both. Further, the bearing units would be required to be spaced apart to control axial and radial loadings when mounted to allow the rolling elements to carry the loadings required. Use of spaced apart separate bearing-units results in longer axial and radial dimensions and therefore an increase in overall volume. Standard ‘off the shelf bearing units as used in this application would be required to be larger physically as the units have to absorb the ‘analysis’ forces, heat dissipation, wear characteristics, pressure distortion & contamination control.